Four (4) tunics (layers) make up the wall.
The alimentary canal is the tubular passage by which food enters the body and through which food residue is eliminated. The anus, large intestine, small intestine, stomach, esophagus and mouth are all parts of the alimentary canal. The four basic tunics (layers) that constitute the walls of the alimentary canal are the mucosa, submucosa, musclaris externa, and serosa. A specific type of tissue that plays an important role in the breakdown of food can be found in each of the layers.
